Near-infrared down-conversion and energy transfer mechanism in Yb³⁺-doped Ba₂LaV₃O₁₁ phosphors

Yb³⁺-doped Ba₂LaV₃O₁₁ vanadate phosphors with near-infrared (NIR) emission are synthesized via the sol-gel method. The phase purity and structure of samples are characterized by X-ray diffraction (XRD). The electronic structure of the self-activated phosphor host Ba₂LaV₃O₁₁ is estimated by density functional theory (DFT) calculation, and the host absorption is mainly ascribed to the charge transition from the O-2p to V-3d states. Photoluminescence emission (PL) and excitation (PLE) spectra, decay curves, absorption spectra and theoretical quantum yields of samples are also investigated. Results indicate that Ba₂LaV₃O₁₁:Yb³⁺ phosphors have strong broad band absorption and efficient NIR emission, which matches well with the spectral response of the Si-based solar cells. The energy transfer processes from [VO₄]^3- to Yb³⁺ and possible transfer models are proposed based on the concentration of Yb³⁺ ions. Results demonstrate that Ba₂LaV₃O₁₁:Yb³⁺ phosphors might act as a promising NIR DC solar spectral converter to enhance the efficiency of the silicon solar cells by utilizing broad band absorption of the solar spectrum.